On Mon, Nov 29, 2010 at 04:24:42PM +0800, Hui Zhu wrote:>On Mon, Nov 29, 2010 at 16:16, Américo Wang <xiyou.wangcong@gmail.com> wrote:>> On Mon, Nov 29, 2010 at 11:56:15AM +0800, Hui Zhu wrote:>>>Hi,>>>>>>Now, there are a lot of ways to debug the Linux kernel with GDB, like>>>qemu, kgtp or kgdb and so on.>>>But the developer more like add a printk. It have a lot of reason, a big one is:>>>(gdb) p ret>>>$3 = <value optimized out>>>>And the code execution order is not right.>>>>>>This is becuase the Kernel is bult with gcc -O2. Gcc will not>>>generate enough debug message with file with -O2.>>>So GDB cannot work very well with Linux kernel.>>>>>>So I make a patch that add a option in "Kernel hacking" called "Close>>>GCC optimization". It will make kernel be built without -O2.>>>>>>I built and use it in i386 and x86_64. I will try to make it OK in other arch.>>>>>>> The problem is that some functions _have to_ be inlined and gcc without -O2>> doesn't inline them. Have check all the cases? I doubt.>>If they really need O2, I set them to O2.>Actually, this is the main work, find out the file that need the O2. :)>>For example:>ifdef CONFIG_CC_CLOSE_OPTIMIZATION>CFLAGS_fpu.o += -O2>CFLAGS_aesni-intel_glue.o += -O2>CFLAGS_ghash-clmulni-intel_glue.o += -O2>endif

No, I didn't mean this, I meant some function that have to be inlinedare those who only work when being inlined, e.g. current_text_addr().

I think it is not alone. :)

Also, since many inline functions sit in hot-path, are there anyperformance regressions with your patch applied?